1. Field of the Invention
This invention relates to a valve for stopping the flow of vapor through a passage in response to the stopping of the flow of liquid in another passage, and more particularly to such a valve having a permanent or constantly energized magnet actuator.
2. Description of the Prior Art
In various applications, it is necessary to control the flow of vapor through a vapor passage in response to the flow of liquid through an adjoining passage. In such applications, the vapor flow must be stopped when the flow of liquid is stopped.
One such application for such a valve is in vapor recovery systems using nozzles of the type used to dispense gasoline or other fuels at service stations. Examples of such nozzles are shown in U.S. Pat. Nos. 4,143,689 issued to Conley et al. and 4,286,635 issued to McMath. Such nozzles have a liquid passage through which fuel flows to the fuel tank of a motor vehicle. Such nozzles also have a vapor passage for the recovery of vapor evacuated from the fuel tank. Such vapor travels from the tank to a vapor recovery storage receptacle. In order to retain the vapor in the storage receptacle, it is important that the vapor passage be closed when the nozzle is removed from the fuel tank.
In the past, vapor check valves have been installed in the vapor passage adjacent to the pump housing to close the vapor passage when the nozzle is removed from the fuel tank. Such check valves have included, for example, a solenoid valve which operates in response to an electrical signal generated by the pump control to close the vapor passage when the pump stops supplying fuel to the liquid passage. However, such valves are expensive and difficult to install. Nonelectrical check valves have also been used in which the valve senses a pressure drop in the liquid passage and shuts off the vapor passage in response thereto. Such valves are relatively expensive and are frequently undependable. If a mechanical connection is provided between the liquid sensing portion and the vapor shut off portion, the connection must be properly sealed. Such seals eventually tend to leak, resulting in fuel leaking into the vapor recovery passage.